Crate lattice_diff 

Pure data layer for Lattice’s diff subsystem.

Arity-agnostic hunk computation over &ropey::Rope inputs, backed by [imara_diff] (Histogram by default; Myers + Patience also wired). No host integration, no actor plumbing – those land in D.2.

compute_diff is the only public engine entry: pass an &[Rope] of N participants (N ∈ {0, 1, 2, 3} in v1), get back a Result<HunkIndex, DiffEngineError>. The engine dispatches by arity to crate-private two-way / three-way algorithms; external consumers never branch on N. See docs/dev/architecture/n-way-diff-membership.md (D.8) for the design rationale.

See docs/dev/architecture/diff-system.md §3.1 for the type model and §4 for the engine choice.

Example

use lattice_diff::{compute_diff, DiffAlgorithm, HunkKind};
use ropey::Rope;

let a = Rope::from("alpha\nbeta\ngamma\n");
let b = Rope::from("alpha\nBETA\ngamma\n");
let hunks = compute_diff(&[a, b], DiffAlgorithm::Histogram)
    .expect("two-way is supported");

assert_eq!(hunks.hunks.len(), 1);
assert_eq!(hunks.hunks[0].kind, HunkKind::Change);

Re-exports

pub use compute::DiffEngineError;

pub use compute::compute_diff;

pub use install::install;

pub use programmatic::ProgrammaticDiffBus;

pub use programmatic::ProgrammaticDiffRequest;

pub use refine::RegionRefinement;

pub use refine::refine_regions;

pub use types::DiffAlgorithm;

pub use types::Hunk;

pub use types::HunkIndex;

pub use types::HunkKind;

pub use types::LineRange;

Modules

compute

Hunk computation: the engine’s single public entry point is compute_diff, which dispatches by participant count to crate-private [two_way] / [three_way] helpers. External consumers (subsystem, benches, integration tests in other crates) go through compute_diff exclusively — no code outside this crate branches on arity. v1 supports N ∈ {0, 1, 2, 3}; N=0 errors as Empty, N=1 returns an empty HunkIndex (dormant session, no peers to diff against), N=2 / N=3 dispatch to the named helpers, N≥4 errors as Unsupported. See docs/dev/architecture/n-way-diff-membership.md (D.8) for the rationale.

filler

D.4.c (2026-05-29) / D.6.b (2026-05-31): hunk-alignment filler rows.

fold

D.3.f.1 (2026-05-29) / DX.3-C7 (2026-06-24): HunkFoldSource.

install

BC.6 / DX.7 / CR.6: the crate-owned install(boot) entry point.

mode

diff-mode minor mode + the host-side bridge that toggles it on participating buffers as DiffSessions open and close.

options

D-fix.5 (2026-06-26): diff-presentation options, owned by the diff subsystem ([[feedback_mode_owns_its_surface]]) rather than host core. Self-register via linkme like every other options! block; the host’s init_from_linkme() walks the global slice at boot, so linking lattice-diff into the binary (it always is — install runs in the Phase-B list) picks these up automatically.

overlay

D.3.a (2026-05-29) — DiffOverlayVirtualRowProvider.

pane_group

D.4.b (2026-05-29) / D.6.b (2026-05-31): HunkRowMapper.

patch

Patch application for round-trip testing.

programmatic

Programmatic diff requests — the host-drained “open a diff and await the user’s verdict” capability that DiffSession::bind_completion was built for.

refine

DR.1 (2026-08-12): intra-line refinement — which part of a changed line changed.

subsystem

D.2.a / D.2.b / D.2.c — DiffSubsystem.

types

Data model for the diff subsystem.